1. Field of Invention
The invention relates to a control circuit board of a terminal device of a host processor and a data processing apparatus, such as a personal computer or a workstation wherein the control circuit board is connected to an input-output connecting slot of the data processing apparatus.
2. Prior Art and Problems
Display systems are typically classified into two types. The display system of the first type is a system called as a main frame interactive (MFI) terminal device or a host connected terminal, as shown in FIG. 8. The MFI terminal device basically includes a control unit 80, a keyboard 81 and a display device 82 which includes a power supply for the control unit 80 and the display device 82 itself. A printer is also connectable to the control unit 80, but the printer is not shown in the FIG. 8 for simplifying the drawing. The control unit 80 includes a microprocessor (MPU) 83, a memory 84, a communication control device 85, a display control device 86 and a system bus 87. The communication control device 85 is connected to a host processor, not shown, through the communication line 87. The operation of the MFI terminal device is controlled by the host processor. More particularly, the host processor decodes an application program to send commands, data, addresses, etc. to the MPU 83 through the communication line 87 and the communication control device 85, whereby the MFI terminal device is directly controlled by the host processor, so that a relatively low performance MPU 83 is used in the MFI terminal device. The host processor requires to display high resolution characters of high quality in various character display modes, such as 80.times.24 character mode, 80.times.32 character mode, 80.times.43 character mode, 132.times.27 character mode, etc. so that a relatively high performance display control device 86 and a high resolution display device 82 are used in the MFI terminal device.
The keyboard 81, the communication line 87 and the display device 82 are connected to the control unit 80 by connectors 88A, 88B and 88C.
The display system of the second type is a system called as a personal computer or a workstation, as shown in FIG. 9. The personal computer basically includes a control unit 90, a display device 91 which includes a power supply for the control unit 90 and the display device itself, a keyboard 92 and a printer 93. The control unit 90 includes an MPU 94, a memory 95, a display control device 96, a keyboard control device 97, a floppy disk control device 98, a hard disk control device 99, a parallel port control device 100, a floppy disk driver (FDD) 101 and a hard disk driver (HDD) 102. The display device 91, the keyboard 92, and the printer 93 are connected to the control unit 90 by connectors 103A, 103B and 103C.
The MPU 94 processes various application programs loaded from the floppy disk drive 101, so that a relatively high performance MPU 94 is used in the personal computer. However, a relatively low resolution display control device 96 and a relatively low resolution display device 91 are used in the personal computer since the application program requires 80.times.25 character mode in maximum in the character mode in the personal computer.
The most of customers install the MFI terminal device in their office at the first step, then install the personal computer for personal use. In other words, the customers separately install the MFI terminal device shown in the FIG. 8 and the personal computer shown in the FIG. 9, so that the cost becomes high and a large space is required in their office. The inventors of the present invention were aware of the above problems, and made the present invention based upon the awareness. The inventors also fixed their eyes upon that the recent control unit 80 of the MFI terminal device could be mounted on a single small circuit board due to the recent technical progress, and the personal computer had input-output connecting (I/O) slots into which various optional circuit boards were connected.
The starting point of the present invention that the circuit board of the control unit 80 of the MFI terminal device is modified to be connectable to the I/O connecting slot of the personal computer is borne by the inventors based upon the above background.
Technical concepts connecting an additional circuit board into the I/O connecting slot of the personal computer have been well known, as shown in Japanese Patent Application 62-94176 (Published Unexamined Patent Application No. 63-259708). The Patent Application No. 62-94176 discloses that an extended function circuit board is connected to a system bus of a personal computer through interface. The personal computer performs basic functions. When the extended function circuit board is connected to the personal computer, the circuit board exchanges programs and data with the personal computer to perform the additional functions. The invention does not reside in such broad concept, but a definite structure as described hereinafter. And, such definite structure is not shown or suggested in the Patent Application 62-94176.